A radio frequency (RF) power amplifier has a variety of applications in the field of wireless data communications. For example, an RF signal transmitter of a mobile telecommunications device is implemented by using the RF power amplifier.
Throughout the generations of mobile telecommunications technology development, the RF power amplifier has been required to support increasingly wider modulation signal bandwidth in order to accommodate increasingly higher speed data communications. For instance, the specification of the long-term evolution (LTE), commonly marketed as 4G LTE, requires a signal bandwidth of up to 20 MHz, which is several times larger than what is required in 3G wideband code division multiple access (W-CDMA) technology.
In designing a wideband RF power amplifier with a wider bandwidth, however, it tends to be more difficult to secure a required linearity within the entire range of the signal bandwidth due to various factors. Also, when discussing phenomena exhibited in relation to such factors, the concept of so-called ‘memory effect’ has been used.
Several solutions have been introduced to secure the required linearity. For instance, certain RF power amplifiers have employed digital predistortion (DPD) technique. However, in case the memory effect becomes severe, the advantage of the DPD technique is limited even after nonlinearity is maximally compensated by the DPD technique.
What is needed, therefore, is an apparatus and/or a method that overcomes at least the shortcomings of the RF power amplifier discussed above.